1. Field of the Invention
This invention relates generally to container systems and, more particularly, to container systems utilizing a container having a neck portion with an opening formed therein for dispensing the contents and a closure cooperating with the neck portion to retain the contents in the container and protect the contents from the ambient environment.
2. Description of the Prior Art
Screw caps or closures fall into two general categories. In the first class the caps have a continuous internal thread which cooperates with a corresponding external thread formed on the external surface of a neck portion or finish of a container. In the second class, caps have a plurality of spaced lugs or have interrupted threads, formed on the internal surface thereof, which cooperate with corresponding cams or interrupted thread segments formed on the external surface of the neck portion or finish of the container. The first class is by far the most common. Examples of the second class are found in U.S. Pat. Nos. 1,612,449 and 4,202,462.
In addition to the two general classes discussed above there are hybrids which use spaced interrupted threads on a closure in combination with continuous threads on a neck portion of a container, or vice versa. U.S. Pat. No. 1,783,314 discloses a closure with interrupted threads for use with a container having continuous threads on the neck portion.
While the invention disclosed herein is useful with the above-discussed container system, it is also useful with other closure/container combinations. For example, U.S. Pat. No. 3,968,823 discloses a container system utilizing a closure having a snap ring retention feature and a container having a neck portion with a detent groove formed therein for receiving the snap ring.
The U.S. Pat. No. 3,968,823 also discloses and discusses heat activatable sealing structures for hermetically sealing the openings of containers. Snap-on closures work well with such hermetic sealing approaches, if modified according to the present invention.
Lug caps, when used with containers with corresponding cam segments, are usually easier to apply and remove than continuous thread caps. One or more complete turns may be required to remove the continuous thread cap from a container, while a fraction of a turn will apply and remove most lug caps. Many lug caps are formed from metal, but metal has problems with corrosion and paint or laquer scratching on the surface. Moreover, such metal caps tend to be more expensive.
A typical unscrewing closure which is molded from synthetic plastic material consists of three main parts--a top wall, a skirt or side wall depending from the top wall and continuous threads formed on the interior wall of the skirt. The top wall, in combination with any desired additional sealing means such as a liner or gasket provides the necessary seal to protect the product in the container from the ambient environment. The threads provide the capability of applying force to hold the closure in its sealing position on the container. The skirt acts as a link between the threads and the top wall.
In many packaging applications the container systems currently available are unsatisfactory. In most container filling applications it is almost inevitable that some product will be spilled on and contaminate the outside of the finish or neck portion, and therefore also the inside threaded portion of a screw cap or closure. When a continuous thread closure is applied, product and/or moisture is trapped in the finish area inside the cap.
Even when no product is spilled on the finish, most filling operations are performed in high moisture areas, causing the trapping of moisture as discussed above. When it is desired to utilize a heat activatable sealing structure, this moisture becomes a contaminant because the moisture cannot escape, can be heated into a vapor stage, and otherwise interferes with the application of the hermetic seal to the container.
With the current prior art container systems, rinse water cannot successfully reach or be drained from the contaminated area. Product trapped in the area promotes growth of bacteria and is generally unsightly. This cannot be tolerated in a food package.